1. Field of the Invention
The present invention relates to a joint structure including a gusset plate and at least one splice plate and a building using the joint structure. The present invention also relates to a method of assembling or reinforcing a building using the joint structure.
2. Description of Background Art
Truss structures for buildings include a column-beam joining part and/or a panel point part. At the location of the column-beam joining part and/or the panel point part, a diagonal member is connected via a gusset plate to an axial force member. The diagonal member can be a structural member or a vibration-damping brace, for example. The axial force member intersects with the diagonal member at a predetermined angle. The gusset plate used in such a joint structure is designed not to cause out-of-plane buckling and/or out-of-plane deformation when a compression force is applied to the diagonal member. Out-of-plane buckling and out-of-plane deformation refer to the plane formed by a smooth side surface of the gusset plate 21, where a splice plate 22 is to be connected as shown in FIG. 2 of the present invention. The plane being referred to is not an inclined joining end edge 30 of the gusset plate 21.
Referring to FIGS. 7A-7D and 8A-8D below, examples of the above joint structure will be described. FIGS. 7A and 7B illustrate a first example according to the background art. FIGS. 7C and 7D illustrated a second example according to the background art. FIGS. 8A and 8B illustrated a third example according to the background art. FIGS. 8C and 8C illustrated a fourth example according to the background art. Each of the above-mentioned figures illustrates a joint structure including a joining end part 4 of a diagonal member 3, such as a structural member or a vibration damping brace, joined with a gusset plate 1 by using a splice plate 2. The end part 4 has a cross-section, which is cruciform in shape, i.e., cross-shaped in cross-section.
In example 1 of the background art illustrated in FIGS. 7A and 7B, a vertical joining plate 5 is fixed on a vertical edge of the gusset plate 1. The vertical joining plate 5 is connectable to a structural member such as a column or one of the axial force members of a truss structure (not shown). The vertical edge of the gusset plate 1 makes a right angle with a bottom horizontal edge of the gusset plate 1. In addition, a horizontal joining plate 6 is fixed on the horizontal edge of the gusset plate 1. The horizontal joining plate 6 is connectable to a structural member such as a beam or the other of the axial force members of the truss structure (not shown). A top horizontal edge 7 extends from the top end of the vertical edge of the gusset plate 1 and a vertical up-right edge 8 extends upward from an end of the bottom horizontal edge of the gusset plate 1 opposite to where the vertical joining plate 5 is fixed. The top horizontal edge 7 and the vertical up-right edge 8 are connected via an inclined joining end edge 10.
A stiffening rib plate 11 is welded at weld 12 on opposite sides of the gusset plate 1 to form a stiffening part with the gusset plate 1. Therefore, the stiffening part has a cross-section, which is cruciform in shape, i.e., cross-shaped in cross-section. The joining end part 4 of the diagonal member 3, which also has a cruciform cross-section, is abutted against the inclined joining end edge 10 of the gusset plate 1. The end edge 10 of the gusset plate 1 is located on the end edge of the stiffening part having a cruciform cross-section. As mentioned above, the diagonal member 3 is, for example, a structural member or a vibration-damping brace.
A splice plate 2 according to the background art is in the form of a rectangular flat plate having a rectangular cross-section. Referring to FIGS. 7B, 7D, 8B and 8D, a portion of each of four splice plates 2 is secured by bolts 13 to each side of the four wings forming the cruciform, i.e., both of the stiffening rib plates 11 and 11 and two portions of gusset plate 1. Each of the splice plates 2 is located on opposite sides of the rib plate 11. The remaining portion of each of the splice plates 2 is secured to each side of the four wings of the joining end part 4 of the diagonal member 3 in the same way as described above.
In example 1 according to the background art, the joining end part 4 of the diagonal member 3 is joined to the gusset plate 1 through the splice plates 2 in the construction described above.
In example 2 according to the background art, as illustrated in FIGS. 7C and 7D, stiffening ribs 14 and 15 are welded to the top horizontal edge 7 and the vertical up-right edge 8 of the gusset plate 1, respectively. In addition, the stiffening rib plate 11 is welded to the gusset plate 1 as described above in the construction according to example 1 of the background art. The stiffening ribs 14 and 15 are used to further prevent out-of-plane buckling or deformation of the gusset plate 1.
FIGS. 8A and 8B illustrate example 3 according to the background art and FIGS. 8C and 8D illustrate example 4 according to the background art. In example 3 illustrated in FIGS. 8A and 8B, the construction is the same as example 1, except that the stiffening rib plate 11 welded to opposite sides of the gusset plate 1 does not extend below a bottom edge of the splice plates 2. In example 4 illustrated in FIGS. 8C and 8D, the construction is the same as example 1, except that the stiffening rib plate 11 welded to opposite sides of the gusset plate 1 extends to the vertical joining plate 5.
In examples 1-4 according to the background art, the stiffening rib plates 11 are welded to opposite sides of the gusset plate 1 so that the gusset plate 1 does not experience out-of-plane buckling and/or out-of-plane deformation when a compression force is applied to the diagonal member 3. However the welding operation takes time, which leads to an increase in the cost of the joint structure and therefore the building in which the joint structure is used.
In addition, if a gusset plate according to the background art is reinforced with a stiffening rib for increasing earthquake resistance, the stiffening rib has to be fixed by welding. Furthermore, if the stiffening rib is welded on site, (1) it leads to an increase in cost, (2) it is subject to the weather, and (3) it may require upward-welding, which results in a low quality weld.
It is necessary to weld the stiffening rib 11 to the gusset plate 1 to compensate for a lack of strength, since the splice plate 2 is in the form of a rectangular flat plate having a rectangular cross-section. The present inventors have determined that a rectangular flat plate does not contribute to a sufficient increase in the buckling strength of the gusset plate 1 to avoid out-of-plane buckling.
The stiffening ribs 14 and 15 welded to the top horizontal edge 7 and the vertical up-right edge 8, respectively, as illustrated in FIG. 7C can increase the buckling strength of the gusset plate 1. However, it is necessary to weld the stiffening ribs 14 and 15 to the gusset plate 1. Accordingly, example 2 of the background art has the same welding problems mentioned above.
As shown in FIG. 8A, if the length of the splice plate 2 contacting the gusset plate 1 on the side surface of the gusset plate 1 is decreased in length, the strength of the joint structure decreases. Accordingly the possibility of out-of-plane buckling and/or deformation increases. As shown in FIG. 8C, if the stiffening rib plate 11 extends to the lower end of the gusset plate 1 to reach the vertical joining plate 5, the strength of the joint structure increases. Accordingly, the possibility of out-of-plane buckling and/or deformation is improved. However, the stiffening rib plate must be welded to the gusset plate 1. Accordingly, the same welding problems described above still remain.
Thus problems in the background art are summarized as follows:
(1). If the stiffening rib plate. 11 for preventing out-of-plane buckling is not fixed to the gusset plate 1, the gusset plate experiences out-of-plane buckling when a compression force is applied to the diagonal member 3. Therefore the stiffening rib plate 11 must be welded to the gusset plate 1 to prevent out-of-plane buckling and/or out-of-plane deformation in the background art.
(2). In the gusset plate 1 with the stiffening rib plate 11, which forms a cruciform cross-section with the gusset plate 1, if the length of the stiffening rib plate 1 fixed to the gusset plate is short, out-of-plane buckling and/or deformation occurs.
(3). A stiffening rib plate 11 welded to the gusset plate 1 is inevitable in the examples according to the background art. The stiffening rib plate must be welded to the gusset plate 1, thereby increasing the cost of the joint structure. Also, if the gusset plate 1 according to the background art is reinforced with a stiffening rib for increasing earthquake resistance, the stiffening rib has to be fixed by welding. Furthermore, if the stiffening rib is welded on site, (1) it leads to an increase in cost, (2) it is subject to the weather, and (3) it may require upward-welding, which results in a low quality weld.